Wireless aerial



Nov. 11, 1952 Filed April 4, 1950 N. M. BE ST WIRELESS AERIAL 2'SHEE'ISSHEET 1' 62M ELM,

in a junction box Patented Nov. 11, 1952 z.

UN I T E AT T a v f ac maa I a f WIR EI IESS AERIALL a H Norman MaxwellBest, London, England, assignor to Antiference Limited, London, England,a?

British company Application April 4, 1950, Serial No. 153,905

. In Great Britain May 6,1949 'n 1 1 The present invention relates to ani mpr oved aerial such as may be used, for example, for the transmissionor reception of wirel-ess waves, and

although not' limited exclusively thereto, partici larly useful for thereception of television signals.

A known form of aerial at present commonly horizontally plane polarisedwaves, the dipole comprises two similar, -hori zontal,, oolinear,spaced, electrically conductive rod-s having their adjacent ends grippedin an insulating junction box whichis held at one endyof a hollowhorizontal supporting arm. The parasitic element, for

example a reflector, may be a single rod or tube or may comprise a pairof similar, horizontal,

, colinear, electrically conductive rods having their adjacentendsconnected together and gripped I h held at the other end of thesupportin n H-formation all in the same horiea ive ln an A pair ofinsulated lea-dasuch as a concentric or twin cable, run from theadjacent ends of the dipole rods to the set.

Such a known aerial is illustrated diagrammatically and in plane view inthe accompanying Figure 1, the dipolerods (12) being shown at 20,

" vide an-aerial which although of receptivity comparable with; orbetter than, known aerial-s, yet

i cheaper to manufacture. Another object is to jprovide an aerial ofhigher selectivity than those now'c-ommonly'in'use for the receptionoftelevisionsi'gnals, without increasing the cost of manufacture ordecreasing the signal strength receivable by the aerial.

Preferred forms of the invention will now be described with reference tothe accompanying drawing, in which 9* Claims. (01. 250-3351),

The dipole, reflector and supporting arm are arranged in Figure 1 showsthe-known form of laerialIdescribedabove, 2

Fi-gure 2 is its polar diagram in a horizontal plane, .i 1 Figure 3 is aplan of one form of aerial,; constructed and arranged to operate inaccordance with this invention, pl I k Figure 4 is the polardiagramgiven jlpy the e lcf Figure N H ,5 Figures 5 and dare respectively aplan and elevatio-n, on a more open scale, of the aerial'shown ri a U. a

Figure '7 is a perspective view, on a yet more open scale, of thejunction box shown in Figures end6,an Figures -8 to 11 inclusive areplan views of various aerials, all of h which are modifications of theaerial of Figure 3, and all lying within the scope of the presentinvention. f a

The aerialillustratedin Figures 3, 5, 6 and 7 comprises a dipole D andparasitic member P in the form of two dipole rods 25, 26 and twoparasitic rods 21, 28, arranged to extend radially in a horizontalplane, from an approximately common centre at equi-angular spacings ofThe four rods are gripped at their inner ends in an insulating junctionbox 29 formed withfour sockets forthis purpose.- I

The junction box is mounted in a bent hollow bracket 30 which is securedto a hollow-mast 3| nected to rod 26-via terminal 33.;

The parasitic rods 21 and Marc connected together by a yoke 36. 4

Twin cables may be used in place of the concentric ones shown; w J

When such an aerial is used to receive wireless waves polarised in ahorizontal :plane, the rods are mounted so asto lie in a horizontalplane and the horizontal polar diagram givenbylone such aerial is shownin Figure 4. It will beseen that "the curve is of cardiac shape rough-1ysimilar-to that of Figure 2 but displaced by with respect thereto.Maximum sensitivity is thu's'given when the parasitic rods point towardsthe source and not, as in the case of the known H-aerlal, when thedipole rods point towards the source.

The polar diagram of Figure 4 applies when of each dipole rod may beabout 5' 9" and of, each director rod about 5 3". The front to" backsensitivity ratio is thenabout 12/1.

With dipole rods 5' 3" and parasitic rods 5' 9" the latter act as areflector-andthe-polar;-

diagram is reversed. The front'to back'ratio is with this arrangementabout 1.5/1.

With an aerial of this kind onlyronejunction, box is required and nosupporting cr.oss=arm..is;-

necessary.

Since its polar diagram is non-circular, l. e., it. has selectivesensitivity, it is preferably arranged" with thedirectionofmaximumsensitivity pointing towards the source; if thereis noappreciable interference-to be taken intoaccount.

I If,- however, there --is a-source or sources of in-' "terference to betaken into consideration,-then a compromise position is adopted with thesource of interferenceas near-aspossible on th'e direction of minimumsignal strength" and the source to-bereceived on the directionof maximumsig- -nal'- strength, but as the relative strengths of the two sourcesafiect the final position-the latter,-- would usually lee-arrived. at bytrial and I error.-

In Figure 8 is shown an aerial similar in all respects to that ofFigures 3 to 7"except that the parasitic rods 38 and 39-are-connected toone of thedipole rods, namely, the-lower rodli).

The advantage or a-know-n-foldeddipolebr ofa-k-nown double v -shapeddipolemay be'applied" to'the novel aerial described above; withreference to Figures *3 to '7.

Thus; asshown in Figure 9, the parasiticrods and 2 6 of Figure-3. have 2been replaced by--a'-- pair -oi'ifolded, but inclined, rods-43 and 444In-the arrangement of Figure 10'both'th'e dipole rods, 45 and 46,and'the parasitic rods, 4 and, are folded.

InFig'ure ll the dipole rods 25 and-'26: offFigure 3 are each replacedby a pair oi-V-shaped rods '49 or '50- respectively. If f desired,- boththe dlpole andparasitic-rods may each be replaced The modificationsdescribed with: reference =-to Figures "'8 to 11 as a-zgeneral rule: do-not giveas high sensitivity asthe:v arrangement of Figures 3.:to 7;but: insome respects have. better: polar diagrams, so that-theymay :beused: with advantagein special circumstances:

The word rod as used herein-is intended: to cover tube-likeras well asrod-dike members Wide variations of the propertiessofiall such aerialscantbe maderby varying-:thelengths of the rods. and-ithei angles:betweenithem- ,and.1byr

placingthe: rods out 10f i a; common plane- Good-reception can :berobtainedlby .placingethe 1 rodssin ,.a, common plane: parallelto.:;th'e: plane ofzpolarisationzrof .theavaves to: be received, and at.9Ilangular intervals about. the common centre;

It has been found, however, that the angle a (Figure 3) between thedipole rods or the angle a between the parasitic rods, may be between 60and without seriously affecting reception, and that the rods can beplaced out of the plane of polarisation without serious diminution ofithezsiginalkstrength: i

What I'claim is:

1. An aerial comprising four rods extending radially from a commoncentre, two being electrically; insulated from each other at theirinner, ends, and the other two being in electric connectionr atitheirinner ends.

2...An1.a.erial comprising four rods supported so that they lie in acommon plane and extend radially-:fromacommon centre, two of the rodsbeing electrically insulated from each other and theother. two beingelectrically connected together.

3. An aerial comprisinga .pair of electrically insulated dipole' rods"inclined obliquely one to the other and apair of electrically connectedparasitic: rods also obliquely; inclined" one to theother;-;thefO'LlIjIOdS being supporte'd' so' that they-liein a commonplane-and -extendradially from a common centre.

4': aerial'asclaimed in claim- 1', wherein theangle between" theelectrically connected-rods lies between fio and "120 5; Anaerial-- asclaimed-"in claim 1; wherein the angle between the electricallyinsulated rods lies between 60" and 120.

6i-An aerial as claimed" in claim 1; wherein the four rods areequiang-ularlyspaced in-a cornmon plane;

7 An aerial asclai-med inclaim*=3 wherein the parasitic rodsareconnected electrically to 'one of the dipole -rods.

8 A' wireless aerial comprising-four electricallyconductiveelements'mounted so that they extend-radially away from acommon centerin a common flatplane,- two adjacent ones being electrically insulatedfrom eachotherand-forming a dipole and the other twobeing "electricallyconnected andform-ing parasitic elements.-

9. A wireless l aerial" comprising four electrically conductive elementsheld at theirinner ends-ina commonsupport so that they extend radiallyaway from thesupport in a commonfiat plane, angles between any twoadjacent elements being between-"60 'and 120} one pair of 'adjacentelements b'eing electrically:insulatedfrom eachother 'so' as toconstituteabent '-'dipo1"' and the-other= pair: being electricallyconnected together so as to form a- -pa'rasiticelen' entn- NORMAN-MZAXWELL BEST.

REFERENCES CITED? I The followingreferences are of -record in" the fileiof ithispatentg" I uNIT'EUs'rATEs-PATENTsT Number. I Name. Date-=1,988,434- Bohnet .al. Jan. 22,1935 2204175 Carter -Junell, 194021368286 Carlson .Jan. 30,-.1945 2;4-19";55'2 1 'Himmel-"etar Apr. 29;.1947

7 452,073 I Schivlyet. al. ..Oct; 26, 1948

